Individually a Rat has a weak bite causing a pretty trivial rupture effect and is easily killed using a pistol.

They are very susceptible to knife blows and frequently this is a more accurate option.

The Rat is a swarm creature and will attack in number posing a more formidable threat to the player.

Rats are able to climb stairs with ease but are unable to climb ladders.

The player should seek higher ground if faced with large numbers of these mutants and pick them off with cheap pistol ammunition. A desk is sufficient.

Against large concentrations, Grenades are not really that effective and may inflict unnecessary damage on the player anyway. Shotguns are certainly effective but many might consider their use to be a waste of resources.

v1.4007 has the Rat behave as a much less formidable swarm creature. The 'pack bite' is virtually non existent and the creatures just tend to run around or pose chittering. Frequently safe to ignore unless the player needs to try for food.

A resident swarm of rats dwell in the scrub to the north of the Sin House. The player may attract the attention of them (and also nearby Blind Dogs and Pseudodogs) and run back into the Sin House to take refuge on a chest of drawers as they pursue. The Sin occupants will respond to the threat, and quite often wound one of their own number.

(Not an option in v1.4007 as the Sin detachment vacate the area early in the game)

The player may take advantage of this in various ways (excluding the possibility of offering assistance, since no dialogue is coded)